1. Field of the Invention
This invention relates to a keyboard, and in particular to a keyboard for a low-cost computing or communications device such as a handheld computer, notebook computer, telephone, smart phone or communicator.
2. Description of the Prior Art
There are many different keyboard designs; all typically rely on the basic principle of a hinged keycap which, when depressed, causes an electrical contact to be completed. Innovations in keyboard design relate to many different performance factors, such as improving tactile response and increasing durability. In addition, the continuing downward price pressure on many consumer devices such as handheld computers requires manufacturers to devise ever cheaper keyboard designs. However, the considerable number of discrete components in conventional keyboard designs, particularly in the hinges of the keys, makes such designs relatively expensive.
A significant challenge is to provide a keyboard design which reconciles the need for economy with good tactile performance, such as adequate key cap travel.
In accordance with the present invention, an electronic device comprises a keyboard in which one or more key caps each overlie a switch, the switch being activated when a key cap is depressed a predetermined amount, in which a key cap is directly joined to a key mat at a first section. By providing for the key cap to be joined (for example, bonded) directly to the key mat, a live hinge is created at the first section, (i.e. a hinge formed from one or more components, some of which deform to allow the hinging action, rather than a conventional hinge in which one component rotates around another). This arrangement is significantly cheaper to manufacture than conventional key hinge arrangements.
The key mat may deform at defined zones to allow the key cap which is joined to it to readily pivot downwards to cause a switch to be closed. Such a design has fewer components than many conventional designs and may therefore be not only considerably cheaper, but also provide good tactile characteristics, such as the length of key travel on depression.
Typically, a part of the keycap is directly joined to the key mat by glue or adhesive tape; this constructional technique is very economical. One or more features, such as channels or grooves, may be present in the key mat near the first section, the or each feature determining the movement of the key cap when depressed, i.e. defining at least in part the structure of the live hinge. Such a feature may also substantially reduce key mat movement under and adjacent to a key cap from having an effect on the key mat under and adjacent to a different key cap and hence, that different key cap itself. Isolation of this kind is conventionally achieved using a bezel around each key cap, which is expensive and unattractive.
In another aspect, there is a key assembly for an electrical device comprising a key cap which overlies a switch, the switch being activated when a key cap is depressed a predetermined amount, in which a key is directly joined to a key mat at a first section.
These and other features of the invention wilt be more fully understood by reference to the following drawings.